7 Things You Didn't Know About Your Friends

Sure, you're up on everything from their favorite soups to their most shameful secrets. But you probably haven't thought much about how your friends are quietly and unassumingly coloring key aspects of your life. While friendships are mostly cherished, few of us are fully aware of the specific effects friends have on our personal growth and happiness.

In my book Friendfluence, The Surprising Ways Friends Make Us Who We Are ($25.95, Doubleday), I survey the ways friends shape our personalities, health, aspirations, values, and habits throughout life. It's a particularly good time to think more consciously about how your friends influence you--for better and for worse--because they are increasingly taking on roles traditionally fulfilled by other kinds of relationships. We're marrying later or not at all, and we're living alone or with friends more than people of previous generations did.

Knowing the minutiae of your pals' tastes and quirks is a privilege, of course. But here are some non-trivial truths about those friends of yours:

Friends are better at describing our behavioral traits than we are, says Simine Vazire, a psychologist who runs the Personality and Self-knowledge Lab at Washington University in St. Louis.
“Friends can assess whether we are funny, dominant, or charming better than we can,” she told me. They are even superior at guessing our IQs. (Good news: It’s often the case that we judge ourselves as less intelligent than we are.)
The reason friends know our behavioral traits and IQs better than we do could be simply that we don’t see ourselves clearly form the inside and/or that these self-judgments can be threatening to our self-esteem, Vazire said.